homelist.py: A Python script to generate a list of user homepages

The purpose of this function is to query the LDAP server and generate a list of (uid, gecos) pairs for each user account.

# - - -   g e n e r a t e A c c o u n t s   - - -

def generateAccounts():
    """Query LDAP for all user accounts.

      [ LDAP_SERVER names TCC's LDAP server and that server is up ->
          return a list of (uid, gecos) tuples for each user
          account, in no particular order ]
    """

First, we bind to the LDAP server. Anonymous binding is sufficient to get the account information we want. See Section 3.3.3, “LDAP_SERVER”.

    #-- 1 --
    # [ LDAP_SERVER names an accessible LDAP server ->
    #     anon  :=  an LDAP object representing an anonymous bind
    #               to LDAP_SERVER ]
    try:
        anon  =  ldap.initialize ( LDAP_SERVER )
        anon.bind ( "", "", ldap.AUTH_SIMPLE )
    except ldap.LDAP_Error, detail:
        print "*** Error, couldn't bind to the LDAP server."
        sys.exit(1)

Next, we use the LDAP module's search function to search first-level children of the node specified by ACCOUNTS_DN. The filterstr argument filters out entries that have no uid attribute. The attrlist argument requests that only the attributes named in the list are returned. See Section 3.3.4, “ACCOUNTS_DN”, Section 3.3.1, “UID_ATTR”, and Section 3.3.2, “GECOS_ATTR”.

    #-- 2 --
    # [ anon is a bound LDAP object ->
    #     ldapResult  :=  a list of LDAP result tuples for
    #         a search of the immediate children of ACCOUNTS_DN that
    #         have a UID_ATTR attribute, containing the UID_ATTR and
    #         GECOS_ATTR attributes ]
    ldapResult  =  anon.search_s ( ACCOUNTS_DN, ldap.SCOPE_ONELEVEL,
        filterstr="(%s=*)" % UID_ATTR,
        attrlist=[UID_ATTR, GECOS_ATTR] )

The structure of ldapResult is described by this excerpt from LDAP programming with Python:

So to produce the return value, we pull out the second element of each tuple in ldapResult to get the attribute map, then form a tuple from the first element of the list for each attribute we want.

There's one more complication: some LDAP entries don't have a GECOS field. In that case we just skip that entry.

    #-- 3 --
    # [ ldapResult is an LDAP-search-format result list ->
    #     resultList  :=  list of (uid, gecos) tuples made from
    #                     ldapResult ]
    resultList  =  []
    for  dn, attrs in ldapResult:
        uid  =  attrs[UID_ATTR][0]
        try:
            gecos  =  attrs[GECOS_ATTR][0]
            resultList.append ( (uid, gecos) )
        except KeyError:
            pass

    #-- 4 --
    return resultList